The present invention relates in general to improving fluid communication between a reservoir formation and a wellbore and more specifically to reducing gas pressure in the perforating gun during perforating operations.
Perforating is a reservoir completion operation that provides fluid communication between a subterranean geological formation and a wellbore, which in turn connects the reservoir to the earth's surface. The goal is to facilitate controlled flow of the fluids between the reservoir formation and the wellbore.
Perforating operations are accomplished by running a perforating gun string down into the wellbore proximate the desired reservoir formation and firing of explosive charges. The explosive charges deposit significant energy into the reservoir formation within microseconds.
While successfully connecting the reservoir to the wellbore, the perforating event can be detrimental to the formation's localized pore structure (permeability) and, hence, the productivity of the formation. The damage to this shock region is typically mitigated by surge flow, wherein the damaged rock is quickly “sucked” into the wellbore. The surge flow is operationally achieved by underbalanced perforating, wherein the wellbore pressure is less than the reservoir pressure.
However, underbalance perforating is not always effective. It has recently been determined that one of the reasons that underbalance perforating may not be effective is due to the “underbalanced environment” temporarily becoming overbalanced resulting in flow of fluid into the reservoir preventing the desired cleaning surge flow. This “dynamic overbalance” is due to the high-pressure gas that may affect the wellbore pressure. In other words, the perforating gun has been a heretofore-neglected component of the perforating environment. Accurate consideration and control of the in-gun pressure is essential for designing and performing an effective perforating operation.
Therefore, it is a desire to provide a method and system for controlling the pressure in a perforating gun during a perforating operation. It is a further desire to provide a method and system for reducing the pressure in a perforating gun post-detonation.